A level 0 incremental backup, which is the base for subsequent incremental backups, copies all blocks containing data.

The only difference between a level0 incremental backup and a full backup is that a full backup is never included in an incremental strategy.

A level 1 incremental backup can be either of the following two types:
========================================================================(1) A differential backup, which backs up all blocks changed after the most recent incremental backup at level 1 or 0
The following command performs a level 1 differential incremental backup of the database:

RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;
———————————————————————————————————————————–(2) A cumulative backup, which backs up all blocks changed after the most recent incremental backup at level 0
The following command performs a cumulative level 1 incremental backup of the database:

Note:
Cumulative backups are preferable to differential backups when recovery time is more important than disk space, because fewer incremental backups need to be applied during recovery.

When deciding how often to take full or level 0 backups, a good rule of thumb is to take a new level 0 whenever 50% or more of the data has changed. If the rate of change to your database is predictable, then you can observe the size of your incremental backups to determine when a new level 0 is appropriate.

The following query displays the number of blocks written to a backup set for each datafile with at least 50% of its blocks backed up: